Updated gems and js libraries. Included Backbone.Marionette and broke the app up into more logical components.
In this commit:

- More/better comments everywhere.
- Better usage of events/models to trigger view changes.
- Now using a call to /posts/all to get both tags/labels and bookmarks.
  (this eliminated the need for a call to /tags/get)
- API module better tracks when to make new calls to /posts/all for updates.
- Looser coupling to the API in AppLayout
- Using a FilteredCollection function to determine which bookmarks to display.
- Header displays a spinner when doing api calls
- various other odds & ends